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[130.180.211.218]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-3912bfdfe61sm19145782f8f.38.2025.03.11.11.42.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Mar 2025 11:42:09 -0700 (PDT) Message-ID: <03c2833d-d80c-4146-911d-8d1a524a2b13@linaro.org> Date: Tue, 11 Mar 2025 19:42:08 +0100 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: TEO as default governor ? To: "Rafael J. Wysocki" Cc: Christian Loehle , "Rafael J. Wysocki" , Linux PM mailing list , Ulf Hansson References: <483602d6-4ac2-4785-b205-912b59fbd6f1@linaro.org> <4a50de85-0deb-4864-b7b5-ee81cec7f167@arm.com> <9b4a15c4-4e0c-43f6-b2ec-e98bc02f67cc@linaro.org> Content-Language: en-US From: Daniel Lezcano In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/03/2025 19:26, Rafael J. Wysocki wrote: > On Tue, Mar 11, 2025 at 7:00 PM Daniel Lezcano > wrote: >> >> On 11/03/2025 18:34, Rafael J. Wysocki wrote: >>> On Tue, Mar 11, 2025 at 5:47 PM Christian Loehle >>> wrote: >>>> >>>> On 3/11/25 16:31, Daniel Lezcano wrote: >>>>> >>>>> Hi, >>>>> >>>>> I think we can agree the teo governor is better then the menu governor. >>>>> >>>>> Would it make sense to make the teo governor the default governor ? >>>>> >>>>> >>>> >>>> Rafael's position seems to be quite conservative here. >>>> Fact is menu is still the default on many systems. >>>> Even worse, the really bad performance disadvantage when >>>> using menu in an intercept-heavy workload has been fixed by Rafael :) >>>> https://lore.kernel.org/lkml/bc7f915b-8d9f-4e05-9939-8b7ecc078f85@arm.com/ >>>> >>>> FWIW I proposed this a while ago: >>>> https://lore.kernel.org/lkml/20240905092645.2885200-3-christian.loehle@arm.com/ >>> >>> It will help if one can make a really convincing case for this change >>> (that is, show that menu with the most recent fixes included is really >>> significantly worse on their platform). >> >> For all the platforms I've been testing, the teo governor is always the >> best one. > > Great! Can you please share any numbers? There are some at a publication doing an evaluation of the irq prediction [1] >> Using the menu governor has also an impact on the user experience as it >> lags on mobile. > > Well, I'm not quite sure what you mean here? For example, the user feels the lag when touching the screen on a mobile or scrolling a document. Changing from menu to teo solves this issue. >> After studying the history of the menu governor few years ago, it >> appeared the menu governor was introduced before the SMP was widely >> used. The strength of the menu governor was the ability to find >> repeating intervals but with he multiplication of the cores, the IPIs >> were introduced which increased the entropy of the busy-idle cycles >> duration, thus making the duration much more random and altering the >> menu governor prediction accuracy. > > While this arguably is the case, menu has also been changed quite a > bit since its introduction. > > What I'm looking for really is a set of numbers showing the difference > and clearly pointing out that teo should be preferred. Ok, let me check if I can find a platform doing energy measurement. I guess x86 is not a good target as the firmware overcomes the kernel decisions right ? -- D. [1] https://hal.science/hal-04095844v1/file/O_S_level_interrupt_prediction_for_performance_and_energy_management_on_Android.pdf -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog